Preemptive Constraint Analysis in Construction Schedules

This paper is set in the context of constraint-based construction alternative scheduling with complex temporal constraints. In construction schedules, the relationships among constraints directly impact the scheduling solution. Conflicting constraints make solving a scheduling problem infeasible, while redundant constraints, especially disjunctive ones, could tremendously increase computation time. Conflicting and redundant constraints hence should be determined in the prescheduling stage to enhance scheduling feasibility and efficiency. In this regard, a constraint integration reasoning framework is developed to identify primary and secondary conflicts and redundancies in schedule constraints. The framework comprises sets of rules for the inference of these conditions within each activity or between two activities. It also computes the feasible range of activity durations, which will be useful for planners in modifying and updating schedules. The framework has been applied to alternative construction scheduling and implemented in ECLiPSe, a constraint logic programming language. An illustrative example of a simplified gas pipe installation project is presented to demonstrate the usage of the framework as a prescheduling constraint analysis tool.